The health of a system can be considered a measure of the condition of a system against expected norms. A healthy system is one whose condition closely matches expectations, whereas an unhealthy system is one whose condition differs from what would be expected, indicating for example deterioration of, or a possible problem with the system. The ability to monitor the health of a system can therefore allow such deterioration and/or problems to be detected and, if necessary, addressed at an early stage.
For example, U.S. Pat. No. 5,684,718 describes a non-real time system for monitoring the operation of an electric generator in which vibration and load data are combined to produce a single signal which is then compared with stored data representative of maximum acceptable combinations of the two parameters. Essentially the system is an automated “look up table” which issues warnings when vibrations have exceeded acceptable limits.
In order to determine the condition, and consequently health, of a system, it is normal to monitor and analyse a series of measurable indicators which themselves reflect aspects of the condition of the system. For instance, taking the example of a gas turbine, one might monitor performance parameters such as turbine and compressor operating temperatures and pressures and spool speeds. To obtain a fuller overall picture of the engine's condition, these performance parameters can be supplemented with further condition indicators including, for example, vibration measurements and measurements of the particulate material entrained in the circulating oil.
Particularly with complex mechanical Systems such as gas turbines, the number of indicators that must be monitored to obtain a useful overall picture of the system's condition can be high. This in turn means that the task of analysing the complete series of indicators to determine the health of the engine is a complex one, typically requiring a skilled expert to analyse the data off-line.
Taking again the example of a gas turbine, it is known for example to collect performance and vibration data from the engine over time to be analysed off-line by one or more experts. Typically the performance data will be compared with simulated data for the same engine and, based on this comparison, an expert will form a view as to the health of the engine. Additionally, a small amount of vibration data will be reviewed, giving a superficial view of gross changes in engine behaviour. If a problem is detected, the vibration data may then be analysed in more detail, often by another expert, to look for any abnormal indications which might be symptomatic of underlying mechanical problems which could lead to a loss of health and operability.